My 11 touring has a Rubes bulb horn, I'm in the process of fixing it and not sure of the reed holder thread size. Measured it and I think it's a 5/8-32 thread but have my doubts that what it is. The reed holder is mounted to the horn not the bulb by the way.
Can one of you model t gurus help me out?
The standard Ford thread is 41/64" x 27 tpi. Late in 1915 they changed to what was probably the industry standard of 5/8" x 28.